The contact of eye tissue with bacteria such as E. coli may lead to various eye infections, such as microbial keratitis. The contact of eye tissue with bacteria may result when an ophthalmic solution contaminated with bacteria is instilled directly in the eye. Examples of such ophthalmic solutions distilled directly in the eye are eye drop solutions (for example, for treating dry eye) or contact lens drop solutions (for example, for wetting a contact lens while worn). Additionally, eye tissue may be contacted with bacteria by placing a contact lens on the eye where the contact lens is contaminated with bacteria. The risk of eye infection is increased when bacteria is adhered to a contact lens, since the bacterial may remain in contact with eye tissue for a prolonged period of time.
For this reason, ophthalmic compositions, such as eye drop and contact lens treating solutions, conventionally include an antimicrobial agent which acts as a preservative, i.e., the preservative inhibits growth of bacteria, as well as other infectious organisms, in case the solution becomes contaminated with such organisms. For contact lens treating solutions, the antimicrobial agents used to preserve the solution may also serve to disinfect contact lenses when rinsed or soaked with the solution. Alternately, ophthalmic compositions may include no preservative, but in such cases, the compositions are packaged in a special container that prevents contamination of the container contents, an example being single unit-dose packages where each dosage of solution is separately packaged.
Various antimicrobial agents are known for use as preservatives in ophthalmic compositions. Such antimicrobial agents should have a broad spectrum of antimicrobial activity and be non-irritating to the eye. However, many antimicrobial agents have a tendency to irritate eye tissue, especially at higher concentrations. Therefore, it is generally advantageous to employ as low as possible concentration of antimicrobial agent to avoid the risk of eye irritation.
U.S. Pat. No. 6,323,165 to Heiler discloses compositions and methods for blocking proteinaceous deposits on hydrophilic contact lenses. The aforementioned compositions contain polyquaternium polymers that selectively bind to lenses and block such deposits.
U.S. Pat. No. 6,274,133 to Hu et al. discloses compositions for treating a silicone-hydrogel contact lens while worn in the eye. The ophthalmic solutions include a cationic cellulosic polymer that binds to the lens and prevents the accumulation of lipids, proteins and other products to the lens, especially during periods of extended wear.
U.S. Pat. No. 4,168,112 to Ellis discloses contact lens solutions especially adapted for rigid gas permeable (RGP) lenses, which contain cationic polymers that coat or form a hydrophilic polyelectrolytic complex on a lens surface. Ellis teaches an approach to solving the problem of protein deposits by trying to prevent proteins from adhering to a contact lens surface in the first place. Such a complex behaves as a hydrogel “cushion” thought to increase the wettability, hydrophilic character and/or comfort of the lens, while reducing a tendency for mucoproteins adherence to a lens surface.
U.S. Pat. No. 4,443,429 to Smith et al. discloses the use in a contact lens disinfecting solution of a dimethyldiallylammonium chloride homopolymer commercially known as Merquat™ 100 (i.e., which has a molecular weight of about 10,000 to about 1,000,000). Preferred disinfecting solution concentrations were recited therein as 0.0004 weight percent to about 0.02 weight percent (4 ppm to 200 ppm).
WO 02/34308 discloses inhibiting adhesion of bacteria to the surface of a biomedical device, such as a contact lens, by binding a cationic polysaccharide to the surface of the device.
It would be desirable to provide an ophthalmic composition with enhanced antimicrobial preservative efficacy that is safe, convenient and economical to use and non-irritating to eye tissue. The present invention is directed to overcoming the problems encountered in the art.